1. Field of the Invention
The present invention relates to a method for the C-terminal degradation of peptides and proteins. More particularly, the invention relates to an efficient method of cleaving a C-terminal thiohydantoin amino acid from a derivatized peptide or protein. The method allows regeneration of the carboxy terminus on the shortened peptide and is effective for multiple reaction cycles. The method results in the production of a hydantoin derivative of the cleaved amino acid which can be detected, e.g., by HPLC. Thus, the method is useful in C-terminal sequencing, as well as other procedures in which controlled degradation from the C-terminus is desired.
2. Background
U.S. Pat. No. 5,059,540, which was issued to Jerome M. Bailey on Oct. 22, 1991 (incorporated herein by reference), traces the development of methods for the sequential degradation of peptides and proteins from the carboxy terminus and contains a review of pertinent literature. That patent describes the use of (1) alkali metal salts of lower trialkylsilanols and (2) trialkylamine-N-oxides as reagents for cleaving C-terminal thiohydantoin amino acids from derivatized peptides and proteins.
While the use of trimethylsilanolate in alcohol has become a preferred method for sequential cleavage of C-terminal amino acids, it nevertheless suffers from certain disadvantages. For example, this reagent is not suitable for an extended number of degradation cycles. Moreover, the method is attended by problems when used in automated sequencing machines, as a result of the formation of precipitates that can clog valves and lines.
Accordingly, a need still exists for an efficient method of cleaving a C-terminal thiohydantoin amino acid from a derivatized peptide or protein.